ORIENTATION' OF MIGRATING ANADROMOUS FISHES 



37; 



The earlier investigations of Cliamberlain 

 (1907) in Alaska also indicated that temperature 

 influenced the selection of streams by sockeye 

 salmon. However, Chamberlain found that the 

 sockeve chose the warmer streams. 



Foerster (1929) observed the migration of sock- 

 eye salmon near Cultus Lake, British Columbia, 

 and found the sockeye at one time entering the 

 colder stream and at another time selecting a 

 warmer stream. He coiicluded that temperature 

 probably had very little directing influence on the 

 upstream migi-ation of the sockeye salmon. 

 Foerster also made measurements of the ;)H and of 

 the dissolved o.xygen in the streams, but was un- 

 able to find any correlation between variations in 

 these factors and tlie selection of streams by the 

 sockeye salmon. 



Roule (1933) expressed the opinion that the 

 i direction of shad, Paralosa nilotica rhodanensis 

 and Alosa alosa, migration was controlled by tem- 

 perature. He pointed out that the migration be- 

 gins -when the river water, pouring into the sea in 

 estuaries, is at a higher temperature than that of 

 the sea. Roule related that in one section of the 

 Rhone River shad fishermen always set their traps 

 on only one bank of the river, whereas along most 

 '- of the river they set traps on both banks. Investi- 

 \ gatiou revealed that the water on one side of the 

 river was several degrees warmer than on the other 

 (hie to the influence of a warm tributary upstream. 

 The shad were always found migrating on the 

 warmer side; and they were also observed to turn 

 off the main stream into certain tributaries which 

 were warmer than the main stream. Roule's ob- 

 servations on the behavior of salmon, Salmo salar, 

 during migration convinced him that the salmon 

 were indifferent to temperature. 



Roule (1914), observing the selection of par- 

 ticular streams by the Atlantic salmon, Salmo 

 solar, in its upstream migration to spawning areas, 

 concluded that the proportion of dissolved Oo in 

 the water was the dominant factor in directing 

 I lie migration. He maintained that the salmon 

 always choose the water with a higher concentra- 

 tion of dissolved O,. Roule (1933) suggested that 

 the metabolic condition of the fish results in in- 

 creased respiratory activity and it becomes polar- 

 ized toward the more highly oxygenated water. 

 Roule used the word "branchiotropism"' to de- 

 scribe deviations in direction brought about by 



respiratory influences. He maintained that the 

 "branchiopolarity" of the salmon drives it forward 

 and acts as its guide. 



Clievey. Roule. and Wrrier (19-27) blamed the 

 depletion of salmon runs in certain streams on the 

 lack of dissolved O, in the streams owing to mill 

 wastes. Their investigations indicated that 

 salmon would not enter a stream with a low dis- 

 solved O2 content. The observation that the shad, 

 Alosa alosa, were not affected by the low O2 con- 

 tent of the water pointed to a marked species 

 difference. 



Russell ( 19.34) did not agree with the findings of 

 Roule a.nd his coworkers. He pointed out that in 

 I he mouths of certain salmon rivers, such as the 

 Tees and the Tyne, there is a long stretch of 

 lieavily polluted water in which the O; content 

 may fall very low. However, salmon enter and 

 ascend these rivers. 



Shelford and Powers (191.5) using a gradient 

 tank technique, found that herring fry, Cliipea 

 pallasi. would orient to differences in tempera- 

 ture and dissolved gases. Powers became con- 

 vinced that gradients of COo tension exert an 

 important influence upon the orientation of mi- 

 grating fishes. Powers and Hickman (1928) 

 measured the CO^, tension in lakes, in rivers drain- 

 ing lakes, and in rivere which did not drain lakes 

 in the Fraser and the Columbia River systems. 

 They found that, in general, lakes and rivers 

 draining lakes had a lower CO.. tension (average 

 0..57 mm. Hg) than rivers not fed by lakes (average 

 1.05 mm. Hg). Further analysis of the data also 

 indicated that typical mountain streams had 

 higher CO, tensions than streams of the lowland. 



Powers (1939) pointed to an observation that 

 the sockeye salmon, given a choice, will always 

 choose the fork of a river which drains a lake. 

 The chinook salmon. Oncorhynchvs fsftaict/tscha, 

 in the same situation apparently is indifferent and 

 moves up either branch. Powers suggested that 

 the sockeye is responding to differences in CO, 

 tension in its selection of a stream draining a 

 lake. The lack of a similar response on the part 

 of the cli'iiook sahniin was juTsiimalily looked 

 upon as a species difference. 



The publications of these investigators who 

 were seeking to correlate the observed movements 

 of migratory fishes to gi-adients of temperature 

 and of dissolved gases were received with great 



